While waiting my message to appear here I had time to experiment. Now I can propose solution too: you can make a role with just those permissions you need to apply for certain service and then let the user has this role for
api_docs app. It worked like that, but was not intuitive to set up that way.
If that is somewhere in docs, i misread it. If it is not, then it would be good to have it, don't you think?
And, like in the other topic: it would be great to adjust automatically the documentation of the API to the same level with permissions.